Compact radio equipment and method of mounting the same

ABSTRACT

A compact radio equipment includes internal circuits on two or more printed circuit boards electrically connected to each other and securely mounted in structure. With this structure, a first metal shield frame is mounted on a first printed circuit board to cover components mounted on the first printed circuit board. A second printed circuit board is mounted on the first metal shield frame.

This application claims priority to prior application JP 2003-313493,the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a compact radio equipment such as acell phone or radio communication terminal, and a mounting methodthereof.

Conventionally, when electric circuits divided into two or more blocksand mounted on two or more printed circuit boards are mounted in theequipment, a first printed circuit board and a second printed circuitboard are electrically connected using one of various kinds ofconnectors or pin contact systems. A frame is mounted between the firstand second printed circuit boards not only to protect the electriccircuits on the first printed circuit board, but also position and fixthe second printed circuit board (see JP-A-2001-111232).

The conventional frame mentioned above is molded of resin, or made fromdie cast alloy. The second printed circuit board is secured with screwsor engaged with hooks. In case of a resin molded frame, a certainthickness is required in the manufacturing process. The increasedthickness of the frame is the cause of preventing the achievement of asmall, thin radio equipment design.

The use of screws to secure the second printed circuit board requires anadditional step of attaching the screws at manufacturing facilities, andthis reduces workability.

On the other hand, the use of hooks to secure the second printed circuitboard causes another problem that the hooked portions are susceptible todamage. The die cast alloy is suitable for making the equipment smalland thin, but manufacturing costs are high. It may also require anadditional step of attaching screws like in the case of resin molding.

Further, the use of a connector or pin contact system to electricallyconnect the electric circuits on the first printed circuit board and theelectric circuits on the second printed circuit board is not enough tosupply adequate ground potential. Therefore, a resin molded frame withaluminum deposited on it is used as a conduction material. In otherwords, metal springs or pins are mounted on the first and second printedcircuit boards so that they will electrically contact the aluminumdeposited frame. Thus, the supply of the ground potential is enhanced.

However, since aluminum deposition is expensive, the cost of a resinmolded frame with aluminum deposited on it becomes high.

Further, since the resin molded frame with aluminum deposited on it isof a contact type, adequate conductivity cannot be obtained. In thiscase, since not only is the supply of the ground potential inadequate,but the thermal conductivity is also insufficient, heat may be built upin a local place.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide compactradio equipment and its mounting method, which can connect two or moreprinted circuit boards and mount them in the equipment in such anefficient manner that can achieve a small, thin equipment design,improve electrical, mechanical, and heat measures, and enable costcutting.

According to the invention of a first aspect, a compact radio equipmentincludes internal circuits on two or more printed circuit boardselectrically connected to each other and securely mounted in structure.

With this structure, a first metal shield frame is mounted on a firstprinted circuit board to cover components mounted on the first printedcircuit board. A second printed circuit board is mounted on the firstmetal shield frame.

Preferably, the second printed circuit board is electrically andmechanically connected to the first metal shield frame so that a bottomsurface layer opposite to a component mounting surface is a groundlayer.

Preferably, the second printed circuit board is electrically connectedto the first metal shield frame so that a bottom surface layer oppositeto a component mounting surface is a ground layer, and the secondprinted circuit board is structured by a radio circuit.

Preferably, a second metal shield frame is provided to cover the secondprinted circuit board. In this event, the second metal shield frame ismounted on the first metal shield frame. Alternatively, the secondshield frame is mounted on the second printed circuit board.

For example, the compact radio equipment serves as a cell-phone or a PHSterminal.

According to the invention of a second aspect, a compact radio equipmentincludes internal circuits on two or more printed circuit boardselectrically connected to each other and securely mounted in structure.

With this structure, a first metal shield frame is mounted on a firstprinted circuit board to cover first components mounted on the firstprinted circuit board. A second metal shield frame is mounted on asecond printed circuit board to cover second components mounted on thesecond printed circuit board. In this case, a first top plate of thefirst metal shield frame and a second top plate of the second metalshield frame are connected to each other.

For example, the compact radio equipment serves as a cell-phone or a PHSterminal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a first embodiment of compactradio equipment to which a mounting method for compact radio equipmentaccording to present invention is applied.

FIG. 2 is a perspective view showing a state in which first electriccircuits, a first shield frame, a second printed circuit board, secondelectric circuits, and a second shield frame, all of which are shown inFIG. 1, are mounted.

FIG. 3 is a perspective view as seen from the bottom side of the secondprinted circuit board of FIG. 1.

FIG. 4 is a structural drawing of the compact radio equipment accordingto the present invention.

FIG. 5 is a block diagram showing the electric circuitry of the compactradio equipment according to the present invention.

FIG. 6 is an exploded perspective view of a second embodiment of compactradio equipment according to present invention.

FIG. 7 is an external perspective view showing a state in which thefirst electric circuits, the first shield frame, the second printedcircuit board, the second electric circuits, and the second shieldframe, all of which are shown in FIG. 6, are mounted.

FIG. 8 is a block diagram showing the operation and structure of thesecond embodiment according to the present invention.

FIG. 9 is an exploded perspective view of a third embodiment of compactradio equipment according to present invention.

FIG. 10 is an external perspective view showing a state in which thefirst printed circuit board, the first electric circuits, the firstshield frame, the second printed circuit board, the second electriccircuits, and the second shield frame, all of which are shown in FIG. 9,are mounted.

FIG. 11 is an exploded perspective view of a fourth embodiment ofcompact radio equipment according to present invention.

FIG. 12 is a structural drawing of the compact radio equipment shown inFIG. 11.

DESCRIPTION OF PREFERRED EMBODIMENTS

At first, brief description will be made of a feature of the presentinvention with reference to drawings.

As shown in FIG. 1, the compact radio equipment according to the presentinvention has such a structure that second electric circuits 211 arearranged on a shield frame 121 mounted over first electric circuits 111on a first printed circuit board 101. In this structure, the firstelectric circuits or radio circuits 111 on the first printed circuitboard 101 is electrically connected with the second electric circuits orradio circuits 211. A second printed circuit board 201-1 is mechanicallysecured to the first printed circuit board 101. This structure makes itpossible to improve the stability of the electric circuits, radioproperties, mechanical strength, and heat radiation efficiency. Comparedwith conventional mounting methods, cheap components can be used, sothat cost-cutting effect is also expected.

In FIG. 1, the first shield frame 121 is mounted over the first electriccircuits 111 on the first printed circuit board 101. The shield frame121 is made of conductive metal, and covers some of the electriccircuits on the first printed circuit board 101 that cause noise or needto avoid the influence of noise, thus improving antinoisecharacteristics.

On the other hand, a second shield frame 221-1 is mounted over theelectric circuits on the second printed circuit board 201-1. The secondshield frame 221-1 is made of conductive metal, and covers all or someof the electric circuits on the second printed circuit board 201-1 thatcause noise or need to avoid the influence of noise, thus improvingantinoise characteristics.

The electric circuits on the first printed circuit board 101 areelectrically connected with those on the second printed circuit board201-1 by a connector 112-1 and a receptor 212-1. The shield frame 121 issoldered to the first printed circuit board 101. The second shield frame221-1 and the second printed circuit board 201-1 are mounted on the topsurface of the first shield frame 121 to improve mounting efficiency. Onthe other hand, the first shield frame 121 and the second shield frame221-1 improve the antinoise characteristics of the electric circuits.

The entire surface layer on the bottom side (that is, the surfaceopposite to the component mounting surface or the side of the secondshield frame 221-1) of the second printed circuit board 201-1 is formedto have ground potential and connected to the first shield frame 121 bya jointing material 331. Since both the shield frames 121 and 221-1 aremade of conductive metal, heat generated from each electric circuit canbe transferred to the printed circuit boards 101, 201-1, and the shieldframes 121, 221-1, and dissipated from each of the electric circuits111, 211 into the printed circuit boards 101, 201-1, and the shieldframes 121, 221-1.

Thus, according to the present invention, among two or more electriccircuits and the printed circuit boards 101, 201-1 with the electriccircuits mounted on them, the first shield frame 121 of conductive metalis mounted over at least some of the electric circuits on the firstprinted circuit board 101. Two or more shield frames of conductive metalare formed to cover at least some of the electric circuits on two ormore printed circuit boards. Then, the two or more shield frames and thetwo or more printed circuit boards are mounted on the first shield frame121 mounted on the first printed circuit board 101. This structure canimprove not only mounting efficiency but also heat radiation efficiencyfrom the electric circuits, thereby improving antinoise characteristicsand electrical properties. Since the shield frames 121 and 221-1 can bemade of stainless steel or phosphor bronze plated with nickel as long asit is conductive metal, cost cutting is also possible.

Upon connecting two or more printed circuit boards, they can be mountedin the equipment in such an efficient manner that can make the equipmentsmall and thin, improve electrical, mechanical, and heat measurescompared to the conventional, and enable cost cutting.

An embodiment of the present invention will now be described withreference to FIG. 1.

In FIG. 1, the second printed circuit board 201 with the second electriccircuits 211 mounted on it and the second shield frame 221-1 formed tocover the second electric circuits 211 are mounted on the top of thefirst shield frame 121 formed to cover at least some of the firstelectric circuits 111 on the first printed circuit board 101. It isnoted here that each of the shield frames 121 and 221-1 has a box shapewith a cover top but no bottom.

Both the shield frames 121 and 221-1 are made of conductive metal thatcan be soldered to each of the printed circuit boards 101 and 201-1, sothat there is no need to use fixation elements like screws to fix eachframe, thereby simplifying the shape of both the shield frames 121 and221-1.

These shield frames 121 and 221-1 can be made from a cheap metal plate,such as of stainless steel or phosphor bronze. Such a metal plate iseasy to machine and hence can reduce manufacturing costs. Further, sincethe metal plate is thin but stiff, it can reduce the total thickness ofthe equipment with high mechanical strength. Each of the shield frames121 and 221-1 covers at least some of the electric circuits not only tosuppress the noise radiated from the electric circuits, but also toshield the electric circuits in the shield frames 121 and 221-1 from thenoise radiated from the other electric circuits. Further, since theprinted circuit boards 101 and 201-1 can be soldered, their conductivityis more improved than contact type boards to increase their thermalconductivity, so that the heat generated from the electric circuits onthe printed circuit board 101 can be dissipated into the shield frames121 and 221-1, and the other printed circuit board 201-1, thus improvingheat radiation efficiency.

The entire surface layer on the bottom side (on the side of the firstshield frame 121) of the second printed circuit board 201-1 is formed tohave ground potential. When the second printed circuit board 201-1 ismounted on the top of the first shield frame 121 and connected to thefirst printed circuit board 101, the electric circuits 111 and theelectric circuits 211 are connected by the connector 112-1 and thereceptor 212-1. The bottom face of the second printed circuit board201-1 and the top plate of the first shield frame 121 are connected bythe jointing material 331. This way of connection improves conductivity,so that the ground potential for the first electric circuits 111 can bemade equal to the ground potential for the second electric circuits 211,thereby improving electrical properties and thermal conductivity.

In case where the second electric circuits 211 are high-frequency radiocircuits, if the bottom face of the second printed circuit board 201-1is brought as close to the top plate of the first shield frame 121 aspossible, the bottom face of the second printed circuit board 201-1 andthe top plate of the first shield frame 121 will be able to function asa capacitor to stabilize RF ground potential.

First Embodiment

Subsequently, description will be made of a first embodiment of thepresent invention.

Structure of First Embodiment

As shown in FIG. 1, the compact radio equipment according to the presentinvention includes the first printed circuit board 101, the firstelectric circuits 111, the first shield frame 121, the second printedcircuit board 201-1, the second electric circuits 211, the second shieldframe 221-1, the connector 112-1, the receptor 212-1, and the jointingmaterial 331.

In addition to these circuit components, the compact radio equipmentshown in FIG. 1 is made up of a main-unit case 1, an antenna 2, abattery 3, switches 4, a display 5, etc.

In FIG. 1, the first electric circuits 111 and the second electriccircuits 211 are electric circuits of the compact radio equipment, andthey are divided into blocks and mounted on two or more printed circuitboards due to limitations on mounting size and electrical properties.

The first printed circuit board 101 and the second printed circuit board201-1 mount the first electric circuits 111 and the second electriccircuits 211, respectively, with signal patterns formed on theirsurfaces or in their internal layers, thus forming the electriccircuitry of the compact radio equipment. The connector 112-1 and thereceptor 212-1 electrically connect the first electric circuits 111 andthe second electric circuits 211 through the power, signal, and groundlines. The connector 112-1 may be a stacking type connector, or of thetype into which a flexible substrate is inserted. In other words, anypart or shape can be used for the connector 112-1 as long as it connectsthe electric circuits 211 on the second printed circuit board 201-1 withthe electric circuits 111 on the first printed circuit board 101.

Although the receptor 212-1 assumes the form of a stacking receptor partattached to the second printed circuit board 201-1, if the secondprinted circuit board 201-1 takes the form of a flexible substrate witha contact terminal area formed on it, there will be no need to attachthe stacking receptor part. Like the connector 112-1, any part or shapecan be used for the receptor 212-1 as long as it connects the electriccircuits 211 on the second printed circuit board 201-1 with the electriccircuits 111 on the first printed circuit board 101.

The second printed circuit board 211 consists of two or more layers.Signal patterns for connection between electric components on the secondelectric circuits 211 are formed on the top surface layer or in theinternal layers. The layer on the bottom side is a ground layer theentire surface of which is covered with an exposed copper foil layer, orplated with gold or nickel, or coated with silver so that it can contactthe first shield frame 121 and the jointing material 331 for conductionof electricity.

In general, compact radio equipment includes electric circuits thatcause noise, such as a high-speed CPU, a step-up charge pump, and aradio transmitter, and electric circuits that are susceptible to noise,such as an analog voice circuit, a radio receiver, and the radiotransmitter. Since these electric circuits are mounted on the sameprinted circuit board or in the same equipment, noise from one electriccircuit may affect another electric circuit. It is therefore practicalto think out the mounting layout that can mount the electric circuits insuch a manner to eliminate interference between the electric circuitsand hence reduce the influence of various types of noise.

The first shield frame 121 combines, into a block, the electric circuitsthat cause noise or the electric circuits that are susceptible to noise,and covers the block. In this case, if the electric circuit blockcovered by the first shield frame 121 is formed in a rectangular shape,the shape of the first shield frame 121 can also be rectangular. Such asimple shape makes it easy to manufacture the first shield frame 121 andhence reduces the cost. It is preferable to solder the first shieldframe 121 to the first printed circuit board 101.

An automatic mounting machine has recently been used to mount electriccircuit components on a printed circuit board. Since such an automaticmounting machine can also be used to mount the first shield frame 121,the mounting cost can also be reduced in the manufacturing process.Solder joints are formed to have ground potential. It is thereforepreferable that the area of the solder joints should be large enough forthe first shield frame 121 to have the same ground potential as thefirst printed circuit board 101. As the ground potential of the firstshield frame 121 gets closer to the ground potential of the firstprinted circuit board 101, the action of the electric circuits coveredby the first shield frame 121 is stabilized, thereby improving antinoisecharacteristics.

Indicated by dashed lines 121′ in FIG. 1 is the mounting location of thefirst shield frame 121 on the first printed circuit board 101.

Like the first shield frame 121, the second shield frame 221-1 combines,into a block, the electric circuits 211 that cause noise or the electriccircuits 211 that are susceptible to noise, and covers the block.Although it is also preferable that the second shield frame 221-1 beformed in a rectangular shape like the first shield frame 121, it may beformed in a different shape according to the limitations on case sizeand the like.

The second shield frame 221-1 is internally mounted on the top plate ofthe first shield frame 121 and soldered to the first shield frame 121.Alternatively, hooks (not shown) may be attached to both of the shieldframes 121 and 221-1 and engaged with each other. In either the casewhere both the shield frames 121 and 221-1 are soldered, or the casewhere they are engaged with hooks, it is preferable that the bottom faceof the second shield frame 221-1 and the top plate of the first shieldframe 121 should contact in a large area, such as to bring the innerside faces of the second shield frame 221-1 into contact with the outerside faces of the first shield frame 121. This reduces the groundpotential difference between both shield frames 121 and 221-1, so thatthe action of the second electric circuits 211 covered by the secondshield frame 221-1 will be stabilized, thereby improving antinoisecharacteristics.

The jointing material 331 is to connect the second printed circuit board201 and the first shield frame 121. In this case, a double-sidedconductive tape is used as the jointing material 331 not only toelectrically connect the second printed circuit board 201 and the firstshield frame 121 in such a manner that they have the same groundpotential, but also to mechanically mount and fix the second printedcircuit board 201-1 onto the first shield frame 121.

Indicated by dashed lines 331′ in FIG. 1 is the mounting location of thejointing material 331 on the outside surface (top surface) of the topplate of the first shield frame 121.

As illustrated in FIG. 2, all the structural components of the presentinvention shown in FIG. 1, namely, the first electric circuits 111, thefirst shield frame 121, and the second printed circuit board 201 (seeFIG. 1), the second electric circuits 211, the second shield frame221-1, and the connector 112-1 (see FIG. 1), and the receptor 212-1 andthe jointing material 331 (see FIG. 1) are mounted on the first printedcircuit board 101.

As shown in FIG. 3, the bottom layer (hatched part 201-1 a in FIG. 3) ofthe second printed circuit board 201-1 is formed in a ground pattern,the entire surface of which is covered with an exposed copper foillayer, or plated with gold or nickel, or coated with silver so that itcan contact the first shield frame 121 and the jointing material 331 forconduction of electricity.

FIG. 4 is a structural drawing of the compact radio equipment accordingto the present invention. It shows a state in which all the structuralcomponents of the compact radio equipment of the present invention, thatis, the first printed circuit board 101 and all the components mountedon the first printed circuit board 101 are arranged in the case 1.

FIG. 5 is a block diagram showing the electric circuitry of the compactradio equipment according to the present invention.

Indicated by dashed lines (121, 221-1) in FIG. 5 are shield frame blocksin each of which an electric circuit covered by each of the shieldframes is named.

Operation of First Embodiment

As shown in FIG. 4, the compact radio equipment includes the printedcircuit boards 101, 201-1 as a structure for its electric circuitry, themain-unit case 1, the antenna 2, the battery 3, the switches 4, and thedisplay part 5. In addition, other unillustrated components, such as aloudspeaker, a vibrator, and a camera, are mounted in the case. Thus,although the compact radio equipment includes lots of components, itmust be compact and thin to keep its portability.

As compact radio terminals grow more sophisticated, the number of partsor components increases. The CPU and its clock frequency also becomefaster. There is also an increased demand for the compact radioequipment typified by a cell phone to have additional functions, whichin turn increases the demand for a technique for mounting both the radiocircuits for the cell phone functions and the radio circuits for theadditional functions. For example, secondary radio circuits for theadditional functions, such as for GPS (Global Positioning System),BLUETOOTH, radio, and television, need mounting.

The cell phone system may vary from country to country, or from providerto provider. In such a case, if the compact radio equipment needs tosupport two or more systems, two or more radio circuits corresponding tothe two or more systems need to be mounted in the compact radioequipment.

Thus, as compact radio equipment grows more sophisticated, morefunctional, and more complex, the demand for smaller, thinner equipmentalso increases. For these reasons, there are the needs to improvemounting efficiency and to reduce or control radio noise increased withthe demand for more sophisticated equipment, as well as cutting the costof the equipment.

Like the printed circuit boards 101 and 201-1 shown in FIG. 1 as astructure for the electric circuitry of the compact radio equipment,electric circuits are divided into two or more blocks and mounted on twoor more printed circuit boards for various reasons. The reasons include:an increasing number of parts or components; mounting limitations due tothe tendency toward smaller, thinner device cases; the demand to avoidthe influence of clock noise increased with an increase in clockfrequency due to the tendency toward high-performance, multifunctionalcompact radio equipment; the need to dissipate heat from electriccircuits, such as the CPU, the charger, and the power supply; andcharacteristic limitations such as the need to divide radio circuitsused at different frequencies or in different systems.

In FIG. 5, a radio circuit corresponds to one of the second electriccircuits 211 of FIG. 1 that are mounted on the second printed circuitboard 201-1. The receptor 212-1 and the connector 112-1 of FIG. 5correspond to the receptor 212-1 and the connector 112-1 of FIG. 1. Acontrol circuit of FIG. 5 corresponds to one of the electric circuits111 of FIG. 1 that are mounted on the first printed circuit board 101.The control circuit includes a CPU and a clock generator circuit, notshown. These electric circuits cause noise that affects other electriccircuits, not shown, such as an analog voice circuit and radio circuits,so that they affect and add constraints to the mounting layout andarrangement of the compact radio equipment.

Measures are taken against the noise sources, such as to step down thepower supply voltage and reduce the generation of noise using a bypasscapacitor, but such measures are often not enough for high-performance,multifunctional, compact radio equipment to prevent noise interference.

Therefore, as shown in FIG. 1, the electric circuits as noise sourcesare mounted in a position to be covered by the first shield frame 121.The first shield frame 121 of conductive metal shields electromagneticwave noise. As a consequence, not only the radiation of noise from theinternal electric circuits can be reduced, but also the influence ofnoise from the outside can be reduced. Further, the first shield frame121 is soldered to the first printed circuit board 101 so that both theradiation of noise and the noise interference can be reduced. Solderjoints are formed to have ground potential. Therefore, if the area ofthe solder joints is large enough for the first shield frame 121 to havethe same ground potential as the first printed circuit board 101, it canbe more resistant to the radiation and interference of noise. Moreover,the first shield frame 121 is mechanically fixed to the first printedcircuit board 101. Thus, the internal electric circuits can beprotected.

The radio circuit is mounted on the second printed circuit board 201-1shown in FIG. 1. The radio circuit in a cell phone is susceptible to CPUnoise or clock noise in the equipment. This causes degradation ofradio-property. If the ground potential of the radio circuit isunstable, the property programmatically tends to be degraded.Particularly, as shown in FIG. 1, if the radio circuit and the controlelectric circuit are connected by the receptor 212-1 and the connector112-1, it is impossible to obtain sufficient ground potential.

Therefore, according to the present invention, the entire surface layeron the bottom side of the second printed circuit board 201-1 is formedas a ground layer, brought into contact with the jointing material 331,and connected to the first shield frame 121. With this structure, thesecond printed circuit board 201-1 with the radio circuit mounted on itcan have the same ground potential as the first printed circuit board101. Therefore, both the printed circuit boards 101 and 201-1 are keptstable in ground potential so that the properties of the radio circuitare improved. In addition, the second shield frame 221-1 is mounted onthe first shield frame 121 so as to cover the second printed circuitboard 201-1. As a consequence, the radiation of noise from the radiocircuit and the noise interference for the radio circuit can be reduced.

In general, the cell phone is provided with a transmitter circuit as aradio circuit, not shown, and a battery charger circuit as a controlelectric circuit. When these electric circuits operate, they generateheat, and during prolonged operation time, the heat is concentratedaround the electric circuits. It is a known fact that metal has goodelectrical conductivity and high thermal conductivity.

According to the present invention, the first printed circuit board 101,the second printed circuit board 201-1, the first shield frame 121, andthe second shield frame 221-1 are electrically connected to one another.Therefore, the conductivity between the structural components is highand the thermal conductivity is improved. Under this circumstance, theheat generated from the transmitter circuit or the charger circuit canbe dissipated into the printed circuit boards 101 and 201-1, and theshield frames 121 and 221-1. Thus, it is possible to improve heatradiation efficiency.

Further, the first shield frame 121 is mounted on the first printedcircuit board 101, and the second printed circuit board 201-1 and thesecond shield frame 221-1 are mounted on the first shield frame 121.This structure enhances mounting efficiency, and hence makes theequipment smaller and thinner. Since there is no need to useconventional resin molded or die-cast frames, the cost of each componentcan be reduced. Moreover, additional elements to fix the components areunnecessary. Thus, the cost of the equipment can be suppressed.

Herein, it is assumed that the radio circuit is a high-frequency circuithaving a bandwidth on the order of GHz. If the second printed circuitboard 201-1 is brought as close to the first shield frame 121 aspossible, the copper foil on the bottom face of the second printedcircuit board 201-1 and the metal plate of the first shield frame 121will be able to function as a capacitor so as to conduct the groundpotential in the RF band. In this case, the jointing material 331 doesnot need to be conductive, and it may be ordinary double-sided tape aslong as it can fix the second printed circuit board 201-1.

Further, if the second printed circuit board 201-1 is soldered andsecured to the first shield frame 121, the double-sided tape to fix thesecond printed circuit board 201-1 is unnecessary, thereby enabling costcutting.

Although the first shield frame 121 is mounted over the control electriccircuit as the noise source on the first printed circuit board 101, thecomponent to be covered may not be a noise source. For example, thefirst shield frame 121, on which the second printed circuit board 201and the second shield frame 221-1 are mounted, may be used as a measureto increase the strength of a CSP type IC. Thus, the structure of thepresent invention may be used to improve mounting efficiency andworkability, and hence to reduce costs, regardless of measures tocontrol noise and heat radiation, and to increase its strength.

In the structure of FIG. 1, although the second shield frame 221-1 ismounted on the first shield frame 121, another structure as shown laterin FIG. 11 may be such that a second printed circuit board 201-3 and asecond shield frame 221-4 are mounted on a jointing material 331 made ofmetal plate, and the jointing material 331 is mounted on the firstshield frame 121.

When the second printed circuit board 201-1 is mounted on the jointingmaterial 331, soldering properties (solder wettability) should beexcellent. In this case, solder joints are provided on the groundpotential layer of the second printed circuit board 201-1 so as toincrease the area of the solder joints. Thus, the jointing material 331,the printed circuit board 201-1, and the second shield frame 221-1 canhave the common ground potential. On the other hand, when the secondshield frame 221-1 is mounted on the jointing material 331, they arepreferably attached to each other with hooks, or soldered to each other.In either case, the area of the hooks or solder joints is increased sothat the jointing material 331 and the second shield frame 221-1 canhave the common ground potential. This structure can not only stabilizethe action of the second electric circuits 211 to improve antinoisecharacteristics, but also dissipate heat from the second electriccircuits 211 into the second shield frame 221-1 and the jointingmaterial 331 to improve heat radiation properties.

The jointing material 331 thus formed is mounted on the first shieldframe 121. It is preferable that the jointing material 331 and the firstshield frame 121 should be attached to each other with hooks, orsoldered to each other. The area of the hooks or solder joints isincreased so that the jointing material 331 and the first shield frame121 can have the common ground potential. Therefore, their groundpotential can also be made equal to the ground potential of the firstprinted circuit board 101. This structure can increase thermalconductivity not only to improve heat radiation efficiency but also makeitself more resistant to the radiation and interference of noise. Thus,the jointing material 331 can be selected from some materials inaccordance with the characteristics of the compact radio equipment.

As described above, if the second printed circuit board 201-1 is coveredby the second shield frame 221-1 and the jointing material 331 from bothsides, the outside surface of the top plate of the second shield frame221-1 may be connected to and mounted on the outside surface of the topplate of the first shield frame 121. In this case, the first shieldframe 121 and the second shield frame 221-1 can serve as a spacer(frame) to combine the first printed circuit board 101 and the secondprinted circuit board 201-1.

FIG. 12 is a structural drawing showing the position of the first shieldframe 121, the second shield frame 221-1, the first printed circuitboard 101, and the second printed circuit board 201 when a metal plateis used as the jointing material 331.

Effects of First Embodiment

As mentioned above, according to the embodiment, the first shield frameis mounted on the first printed circuit board, and the second printedcircuit board and the second shield frame are mounted on the firstshield frame. In this manner, mounting efficiency is improved so as toachieve a smaller, thinner radio terminal design.

The first shield frame 121 and the second shield frame 221-1 are mountedto cover the radio circuits or noise sources, and the electric circuitsthat are susceptible to noise. As a consequence, radio properties andantinoise characteristics are improved.

Further, the shield frames are formed in a box shape (boxcover shape),and each of the printed circuit boards can be connected to each of theshield frames. This makes it possible to efficiently dissipate heat fromthe electric circuit components on the print circuit boards and hence toimprove heat radiation efficiency.

In addition, conductivity between each shield frame and each printedcircuit board is enhanced. Therefore, they can have the same groundpotential so as to improve the properties of the radio circuits and theelectric circuits and to stabilize the action of each circuit component.

Since the shield frames are made of metal, not only they can bemanufactured at low cost, but also the printed circuit boards and theshield frames can be easily connected and secured to each other. Thus,manufacturing costs can be reduced.

Specifically, the shield frames are made by forming a metal plate into abox shape (boxcover shape). Therefore, they can protect the electriccircuit components on the printed boards, and can also reinforce theprinted circuit boards. Thus, the strength of the equipment can beimproved.

As described above, the compact radio equipment according to the presentinvention can simultaneously meet lots of improvement requirements, suchas to make the equipment smaller and thinner, improve mountingefficiency, stabilize the action of the radio circuits and the electriccircuits, improve the fixation of two or more printed circuit boards,workability in the manufacturing process, the protection of the electriccircuit components on the printed circuit boards, and heat radiationefficiency, reduce costs, etc.

Second Embodiment

Subsequently, description will be made of a second embodiment of thepresent invention.

Structure of Second Embodiment

In FIG. 6, similar members to those shown in the first embodiment areused for the first printed circuit board 101, the first electriccircuits 111, the first shield frame 121, the second printed circuitboard 201-1, the second electric circuits 211, a second shield frame221-2, a connector 112-2, and the jointing material 331.

In the first embodiment, the second shield frame 221-1 is mounted on thefirst shield frame 121. On the other hand, in the second embodiment, thesecond shield frame 221-2 is mounted on the first printed circuit board101 as shown in FIGS. 6 and 7 to cover the first shield frame 121 andthe connector 112-2 together with the second printed circuit board 201-1with the second electric circuits 211 mounted on it. Indicated by dashedlines 221′ in FIG. 6 is the mounting location of the second shield frame221-2 on the first printed circuit board 101.

As also described in the first embodiment, the second printed circuitboard 201-1 takes the form of a flexible substrate. In this case, it hasa contact terminal area 212-2 instead of the receptor. The contactterminal area 212-2 is inserted into the connector 112-2 to connect thefirst electric circuits 111 and the second electric circuits 211 throughthe power, signal, and ground lines. Like in the first embodiment, thebottom layer of the second printed circuit board 201-1 is formed in aground pattern, the entire surface of which is covered with an exposedcopper foil layer, or plated with gold or nickel, or coated with silverso that it can contact the first shield frame 121 and the jointingmaterial 331 for conduction of electricity.

FIG. 7 is an external perspective view showing a state in which all thecomponents shown in FIG. 6, namely, the first electric circuits, thefirst shield frame, the second printed circuit board, the secondelectric circuits, and the second shield frame are mounted. In otherwords, FIG. 7 shows a state in which all the structural components ofthe present invention shown in FIG. 6, namely, the first electriccircuits 111, the first shield frame 121, the second printed circuitboard 201, the second electric circuits 211, the second shield frame221-2, the connector 112-2, the contact terminal area 212-2, and thejointing material 331 are mounted on the first printed circuit board101.

Operation of Second Embodiment

FIG. 8 is a block diagram showing the operation and structure of thesecond embodiment of the present invention.

Cell phones are a typical example of the compact radio equipment. Withthe recent speed increase in cell phone systems, equipment with two ormore radio circuits has been commercially available to meet the need touse both of conventional and next-generation cell phone systems.Referring to FIG. 8, such compact radio equipment with two or more radiocircuits will be described.

In FIG. 8, a second radio circuit corresponds to one of the secondelectric circuits 211 of FIG. 6 that are mounted on the second printedcircuit board 201-1. The contact terminal area 212-2 and the connector112-2 of FIG. 8 correspond to the contact terminal area 212-2 and theconnector 112-2 of FIG. 6. A control electric circuit, a chargerelectric circuit, a clock electric circuit, and a first radio circuit ofFIG. 8 correspond to the electric circuits 111 of FIG. 6 that aremounted on the first printed circuit board 101.

In the second embodiment, the first radio circuit is mounted as shown inFIG. 6 in a position to be covered by the first shield frame 121. Thefirst shield frame 121 is made of conductive metal to shieldelectromagnetic wave noise, so that not only can the radiation of noisefrom the internal electric circuits be reduced, but the influence ofnoise from the outside can also be reduced. The first shield frame 121is soldered to the first printed circuit board 101. In this manner, boththe radiation of noise and the noise interference can be reduced. Inthis event, solder joints are formed to have ground potential.Therefore, if the area of the solder joints is increased, the firstshield frame 121 can have the same ground potential as the first printedcircuit board 101. Thus, thermal conductivity can be increased not onlyto improve heat radiation efficiency but also to make the equipment moreresistant to the radiation and interference of noise. Thereby, theaction of the first radio circuit is stabilized so as to improve itsproperties.

Further, the first shield frame 121 is mechanically secured to the firstprinted circuit board 101 so as to protect the internal electriccircuits.

The second radio circuit is mounted on the second printed circuit board201-1 shown in FIG. 6. The entire surface layer on the bottom side ofthe second printed circuit board 201-1 is formed as a ground layer,brought into contact with the jointing material 331, and connected tothe first shield frame 121. This allows the second printed circuit board201-1 with the second radio circuit mounted on it to have the sameground potential as the first printed circuit board 101. Therefore,their ground potentials remain stable so as to improve the properties ofthe second radio circuit. Further, heat generated from the first radiocircuit, the second radio circuit, and the other electric circuits onthe first printed circuit board 101 can be dissipated into the shieldframes 121, 221-2. Thus, heat radiation efficiency can be improved.

In the first embodiment shown in FIG. 1, the second shield frame 221-1is mounted on the first shield frame 121 with the connector 112-1 andthe receptor 212-1 mounted outside the second shield frame 221-1.

On the other hand, in the second embodiment shown in FIG. 6, the secondshield frame 221-2 is formed to cover the connector 112-2 and theterminal connection part 212-2 together with the second printed circuitboard 201-1, and mounted on the first printed circuit board 101. Thesecond shield frame 221-2 is mounted on the first printed circuit board101 so as to cover the second printed circuit board 201-1, the connector112-2, and the terminal connection part 212-2. Therefore, the radiationof noise from the second radio circuit and the noise interference withthe second radio circuit can be reduced.

Further, if the second shield frame 221-2 covers the first shield frame121 in such a manner that the inner side faces of the second shieldframe 221-2 are brought into contact with the outer side faces of thefirst shield frame 121, their ground potential effects can be furtherenhanced. Consequently, thermal conductivity is increased to furtherimprove heat radiation efficiency.

In the second embodiment, the first shield frame 121 with the secondprinted circuit board 201-1 mounted on it is mounted on the firstprinted circuit board 101, and the second shield frame 221-2 is mountedon the first printed circuit board 101 in such a manner to cover thefirst shield frame 121 with the second printed circuit board 201-1mounted on it. This structure enhances mounting efficiency and hencemakes the equipment smaller and thinner.

Since the compact radio equipment of the second embodiment can bemanufactured without use of conventional resin molded or die-castframes, the cost of each component can be reduced. Moreover, additionalelements to fix the components are unnecessary and therefore, the costof the equipment can also be reduced.

Third Embodiment

Subsequently, description will be made of a third embodiment of thepresent invention.

Structure of Third Embodiment

Referring to FIG. 9, description will be made of a structure of a thirdembodiment according to the present invention.

In FIG. 9, similar members to those shown in the first embodiment areused for the first printed circuit board 101, the first electriccircuits 111, the first shield frame 121, a second printed circuit board201-2, the second electric circuits 211, a second shield frame 221-3,the connector 112-1, the receptor 212-1, and the jointing material 331.

In the first embodiment, the second shield frame 221-1 is mounted on thetop plate of the first shield frame 121 in such a manner to cover thesecond electric circuits 211 and the second printed circuit board 201-1.On the other hand, in the third embodiment shown in FIGS. 9 and 10, thesecond shield frame 221-3 is mounted on the second printed circuit board201-2 with the second electric circuits 211 mounted on it.

FIG. 10 is an external perspective view showing a state in which all thecomponents shown in FIG. 9, namely, the first printed circuit board, thefirst electric circuits, the first shield frame, the second printedcircuit board, the second electric circuits, and the second shield frameare mounted.

When the second printed circuit board 201-2 is mounted on the outsidesurface of the top plate of the first shield frame 121 through thejointing material 331, a double-sided conductive tape is used as thejointing material 331. Alternatively, the second printed circuit board201-2 may be soldered onto the outside surface of the top plate of thefirst shield frame 121. As mentioned in the first and secondembodiments, if the second electric circuits 211 are high-frequencyelectric circuits, the jointing material 331 may be ordinarydouble-sided tape.

Operation of Third Embodiment

The first shield frame 121 of conductive metal shields electromagneticwave noise, so that not only can the radiation of noise from the firstelectric circuits 111 be reduced, but the influence of noise from theoutside can also be reduced. The first shield frame 121 is soldered tothe first printed circuit board 101. In this manner, both the radiationof noise and the noise interference can be suppressed. In this event,solder joints are formed to have ground potential. Therefore, if thearea of the solder joints is increased, the first shield frame 121 canhave the same ground potential as the first printed circuit board 101,and consequently, it can be more resistant to the radiation andinterference of noise. This makes it possible not only to stabilize theaction of the electric circuits and improve their properties, but alsoto further improve thermal conductivity and heat radiation efficiency.Moreover, the first shield frame 121 is mechanically secured to thefirst printed circuit board 101, and therefore, the internal electriccircuits can be protected.

The second electric circuits 211 are mounted on the second printedcircuit board 201-2. The entire surface layer on the bottom side of thesecond printed circuit board 201-2 is formed as a ground layer, broughtinto contact with the jointing material 331, and connected to the firstshield frame 121. This allows the second printed circuit board 201-2with the second electric circuits 211 mounted on it to have the sameground potential as the first shield frame 121 and the first printedcircuit board 101. Therefore, their ground potentials remain stable soas to improve the properties of the second electric circuits 211. Thesecond shield frame 221-3 is soldered to the second printed circuitboard 201-2, so that both the radiation of noise and the noiseinterference can be reduced. In this event, solder joints are formed tohave ground potential. If the area of the solder joints is increased,the second shield frame 221-3 can have the same ground potential as thesecond printed circuit board 201-2, and it can be more resistant to theradiation and interference of noise. Thus, not only is the action of theelectric circuits stabilized to improve their properties, but thethermal conductivity is also increased to improve heat radiationefficiency.

In the third embodiment, the second shield frame 221-3 is formed tocover the second electric circuits 211 on the second printed circuitboard 201-2, and mounted on the second printed circuit board 201-2. Thesecond printed circuit board 201-2 is mounted on the top plate of thefirst shield frame 121. Therefore, the second printed circuit board201-2 can have the same ground potential as the first shield frame 121and the first printed circuit board 101. Thus, it can be more resistantto the radiation and interference of noise so as to stabilize the actionof the electric circuits and improve their properties. Under thiscircumstance, the second printed circuit board 201-2 is soldered ontothe first shield frame 121 so that both the radiation of noise and thenoise interference can be further suppressed. Solder joints are formedto have ground potential. Therefore, if the area of the solder joints isincreased, the second printed circuit board 201-2 can have the sameground potential as the first shield frame 121 and the first printedcircuit board 101. In this manner, it can be more resistant to theradiation and interference of noise. As a consequence, not only is theaction of the electric circuits stabilized to improve their properties,but the thermal conductivity is also increased to improve heat radiationefficiency.

The entire surface layer on the bottom side of the second printedcircuit board 201-2 is formed as a ground layer. It is assumed that thesecond electric circuits 211 are high-frequency radio circuits. If thedistance between the second printed circuit board 201-2 and the firstshield frame 121 is lessened, the copper foil on the bottom face of thesecond printed circuit board 201-2 and the metal plate of the firstshield frame 121 will be able to function as a capacitor to conduct theground potential in the RF band. In this case, the jointing material 331does not need to be conductive, and it may be ordinary double-sided tapeas long as it can fix the second printed circuit board 201-2. Further,if the second electric circuits 211 are high-frequency radio circuits,the second printed circuit board 201-2 can be soldered and secured tothe first shield frame 121. In this case, the double-sided tape to fixthe second printed circuit board 201-2 is unnecessary, thereby enablingcost cutting.

Fourth Embodiment

Subsequently, description will be made of a fourth embodiment of thepresent invention.

Structure of Fourth Embodiment

Referring to FIG. 11, description will be made of a structure of afourth embodiment according to the present invention.

As shown in FIG. 11, the compact radio equipment according to thepresent invention includes the first printed circuit board 101, thefirst electric circuits 111, the first shield frame 121, a secondprinted circuit board 201-3, the second electric circuits 211, a secondshield frame 221-4, the connector 112-1, the receptor 212-1, and thejointing material 331.

A different point between the compact radio equipment shown in FIG. 11and the compact radio equipment shown in FIG. 1 is that the top plate ofthe first shield frame 121 and the top plate of the second shield frame221-4 are joined together in such a manner that the component mountingside of the first printed circuit board 101 and the component mountingside of the second printed circuit board 201-3 face each other.

As shown in FIG. 12, the compact radio equipment shown in FIG. 11 alsoincludes the main-unit case 1, the antenna 2, the battery 3, theswitches 4, and the display part 5.

In FIG. 11, the first electric circuits 111 and the second electriccircuits 211 are electric circuits of the compact radio equipment, andthey are divided into blocks and mounted on two or more printed circuitboards due to limitations on mounting size and electrical properties.

The first printed circuit board 101 and the second printed circuit board201-3 mount the first electric circuits 111 and the second electriccircuits 211, respectively, with signal patterns formed on theirsurfaces or in their internal layers. Thus, the electric circuitry ofthe compact radio equipment is formed. The connector 112-1 and thereceptor 212-1 electrically connect the first electric circuits 111 andthe second electric circuits 211 through the power, signal, and groundlines. The connector 112-1 may be a stacking type connector, or of thetype into which a flexible substrate is inserted. In other words, anypart or shape can be used for the connector 112-1 as long as it connectsthe electric circuits 211 on the second printed circuit board 201-3 andthe electric circuits 111 on the first printed circuit board 101.

Although the receptor 212-1 assumes the form of a stacking receptor partattached to the second printed circuit board 201-3, if the secondprinted circuit board 201-3 takes the form of a flexible substrate witha contact terminal area formed on it, there will be no need to attachthe stacking receptor part. Like the connector 112-1, any part or shapecan be used for the receptor 212-1 as long as it connects the electriccircuits 211 on the second printed circuit board 201-3 with the electriccircuits 111 on the first printed circuit board 101.

Operation of Fourth Embodiment

The first shield frame 121 of conductive metal shields electromagneticwave noise. Thus, not only can the radiation of noise from the firstelectric circuits 111 be reduced, but the influence of noise from theoutside can also be reduced. The first shield frame 121 is soldered tothe first printed circuit board 101 so that both the radiation of noiseand the noise interference can be reduced. Solder joints are formed tohave ground potential. Therefore, if the area of the solder joints isincreased, the first shield frame 121 can have the same ground potentialas the first printed circuit board 101. As a consequence, it can be moreresistant to the radiation and interference of noise. This makes itpossible not only to stabilize the action of the electric circuits andimprove their properties, but also to further improve thermalconductivity and heat radiation efficiency. Moreover, the first shieldframe 121 is mechanically secured to the first printed circuit board101. Therefore, the internal electric circuits can be protected.

The second electric circuits 211 are mounted on the second printedcircuit board 201-3. The entire surface layer on the bottom side of thesecond printed circuit board 201-3 is formed as a ground layer, broughtinto contact with the jointing material 331, and connected to the firstshield frame 121. This allows the second printed circuit board 201-3with the second electric circuits 211 mounted on it to have the sameground potential as the first shield frame 121 and the first printedcircuit board 101. Therefore, their ground potentials remain stable soas to improve the properties of the second electric circuits 211. Thesecond shield frame 221-4 is soldered to the second printed circuitboard 201-3. In this manner, the radiation of noise and the noiseinterference can be suppressed. Solder joints are formed to have groundpotential. If the area of the solder joints is increased, the secondshield frame 221-4 can have the same ground potential as the secondprinted circuit board 201-3. As a consequence, it can be more resistantto the radiation and interference of noise, Thus, not only is the actionof the electric circuits stabilized to improve their properties, but thethermal conductivity is also increased to improve heat radiationefficiency.

In the fourth embodiment, the second shield frame 221-4 is formed tocover the second electric circuits 211 on the second printed circuitboard 201-3, and mounted on the second printed circuit board 201-3.Since the second printed circuit board 201-3 is mounted on the jointingmaterial or connection board 331, the second printed circuit board 201-3can have the same ground potential as the first shield frame 121 and thefirst printed circuit board 101. Therefore, it can be more resistant tothe radiation and interference of noise. Thereby, the action of theelectric circuits is stabilized so as to improve their properties. Inthis event, the second printed circuit board 201-3 can be soldered ontothe connection board 331 to further reduce both the radiation of noiseand the noise interference. Solder joints are formed to have groundpotential. Therefore, if the area of the solder joints is increased, thesecond printed circuit board 201-3 can have the same ground potential asthe first shield frame 121 and the first printed circuit board 101.Consequently, it can be more resistant to the radiation and interferenceof noise. Thus, not only is the action of the electric circuitsstabilized to improve their properties, but the thermal conductivity isalso increased to improve heat radiation efficiency.

The entire surface layer on the bottom side of the second printedcircuit board 201-3 is formed as a ground layer. It is assumed here thatthe second electric circuits 211 are high-frequency radio circuits. Ifthe distance between the second printed circuit board 201-3 and topplate of the second shield frame 221-4 is lessened, the copper foil onthe bottom face of the second printed circuit board 201-3 and the metalplate of the second shield frame 221-4 will be able to function as acapacitor to conduct the ground potential in the RF band.

As described above, the present invention is applicable to compact radioequipment, such as a cell phone or PHS (Personal Handyphone System), andits mounting method, in which internal electric circuits are mounted ontwo or more printed circuit boards electrically connected to each otherand securely mounted in the structure.

While the present invention has thus far been disclosed in conjunctionwith several embodiments thereof, it will be readily possible for thoseskilled in the art to put the present invention into practice in variousother manners.

1-18. (canceled)
 19. Compact radio equipment, comprising: a first metalshield frame mounted on a first printed circuit board to cover a firstcomponent mounted on the first printed circuit board; and a second metalshield frame mounted on a second printed circuit board to cover a secondcomponent mounted on the second printed circuit board, wherein a firsttop plate of the first metal shield frame and a second top plate of thesecond metal shield frame are connected so as to face each other.
 20. Amethod of mounting compact radio equipment comprising the steps of:mounting a first metal shield frame on a first printed circuit board tocover a first component mounted on the first printed circuit board; andmounting a second metal shield frame on a second printed circuit boardto cover a second component mounted on the second printed circuit board,wherein a first top plate of the first metal shield frame and a secondtop plate of the second metal shield frame are connected so as to faceeach other.